Flashcards in Antifungals and antivirals Deck (27):
What are the four important stages of the viral lifecycle?
Enveloped virus invades the host cell.
The viral nucleic acid is released and replicated
Viral nucleic acid is repackaged
Envelope proteins are used to package the caspid protein and nucleic acid, and release them from the cell
Name some common acute/relapsing viral infections.
Herpesviruses (HSV, VZV and CMV)
Name some chronic active viral infections.
These are the most commonly treated.
Herpes viruses (Hep B and C)
What is the principle drug used against herpes infections?
Aciclovir - principally HSV and VZV
- useful in treatment and prophylaxis
How does Aciclovir work?
It requires activation by an enzyme which is only found within virally active cells.
The ACV molecule is then inserted into DNA replication (nucleotide analogue), which disrupts viral multiplication
Describe the possible toxic effects of Aciclovir.
Low doses - well tolerated
High doses - when treating herpes simplex encephalitis
- renal tubular crystalosis
What are neuroaminidase inhibitors?
A class for acute viral infections that prevent the action of neuroaminidase in viral budding
When should neuroaminidas inhibitors be used?
In the elderly to shorten the duration of influenza symptoms
- young people can survive with symptoms for a few days
Can be used as post-exposure prophylaxis
What are the possible toxic side effects of neuroaminidase inhibitors?
Usually well tolerated
Neuropsychiatric symptoms (especially in Japan)
Probably safe in pregnancy
What are the efficacy concerns in regards to neuraminidase inhibitors?
Not as good as antibiotics
Can't achieve cure in a chronic active infection
Fungal infections can come in which two forms?
Yeasts - mostly candida's
Moulds - commonly arising in immunocompromised patients
Describe the components of a fungal cell wall?
Cell membrane bilayer
Why is targeting antifungal treatment hard?
Fungal cells are very similar to human cells, and we don't want treatments to attack the healthy cells in a patient
List some antifungal treatments that are applied topically.
How do topical antifungals work?
They all inhibit the synthesis and function of ergosterol.
- a component of the plasma cell membrane bilayer in fungi
What are the pros and cons of topical therapy?
Pros - relatively non-toxic
Cons - limited efficacy for anything other than a mild infection
When would terbinafine given orally instead of topically?
In more serious fungal infections as it achieves much higher doses in the skin and nails than
Describe oral terbinafine.
A highly lipophilic drugs that accumulates in the skin and nails after systemic administration
What are some of the toxic effects of oral terbinafine?
Can cause hepatic upset and SJS
What are the systemic agents used for severe fungal infections?
What do azoles do?
They inhibit synthesis of ergosterol - important components of the plasma membrane on fungal cells
What is the most common Azole to prescribe?
Fluconazole is the most common, but there are other more broad spectrum agents available
What fungi are Fluconazole active against?
Other Azoles however, are active against moulds
Give an example of an Echinocandin?
Describe Caspofungin, including its spectrum, mechanism of action, resistance and toxicity.
Broad spectrum antifungal agent
Inhibits glucan formation in the fungal cell walls
Excellent sepctrum against candida and aspergillus
Describe Amphotericin B, including its spectrum, mechanism of action and toxicity.
The boradest spectrum anti-fungal agent
Forms membrane attack complexes and permeabilises fungal membrane
Limited to specialist use